Heat motor



, Oct 8, 1968 W. H. CHURCHILL ETAL 9 5 HEAT MOTOR Filed March 1, 1967 2 Sheets-Sheet l Inveniars. Wilmer If. Ciau'ciwllz flrmazzdo J. Garcia DougZas .B. Leaihem- M12202 Wrz'gizi, 5 MW 22 Oct. 8, 1968 I I w. H. CHURCHILL ETAL 3,404,530

HEAT MOTOR Filed March 1, 1967 2 Sheets-Sheet 2 man-s1 Wm? 11. 6721147010221 flrimzuio Idaralz Douglas B. Leaikem &

ABSTRACT OF THE DISCLOSURE i iThis invention is directed at an electrically actuated transducer which has a looped heating element circumscribing a movable shaft and embedded in a thermally responsive material. The thermally responsive material may include a wetting agent.

Background of the invention Prior to the present invention, many known transducers of heat motors were activated solely by environmental temperatures which restricted the range of possible applications severely, while the present invention is an electrically activated transducer and, not dependent on environmental conditions; it therefore is suitable for use in electronic feedback systems.

One ofthe more serious problems of the heat motor art is to prevent the thermal material from leaking from the motor during operation, particularly along the piston surfaces. One method of preventing this problem is to provide aflexible envelope,- known as a boot, which surrounds the piston and'separates the piston from the thermal material. 7 i

The rate of'response of boot type heat motors is comparat ively slow due to power input limitations, in addition, flexible boot materials tend to deteriorate when subjected to the sudden heat of a high power, internal heater element. V

Another means of overcoming the sealing problem is to place the piston in a chamber separate from the thermal material with a flexible diaphragm therebetween, so that when'the thermal material expands, pressure is exerted againstthe diaphragm and thence against the piston. The diaphragm configuration places a definite limit on the allowable piston travel or displacement.

The prior art, where the'bootor envelope type seal was not used, utilizedcompound seals which basically require that one seal in effect backs up another seal. The material from which each of the multiple seals are made is usually different, in order to accomplish different functions suchas wiping and pressure sealing.

Heat motors having an external heater (heat elements.

which are located outside of the thermal material, and

United States Patent O quite frequently outside-the housing which contains the thermal material) also respond slowly. The reason for the slow response of heat motors having external heater assemblies is that in order to heat the thermal material, it is necessary that the heat pass from the elements through the housing to the material and must heat the material from the outside in. Further, on cooling, the heat must reverse the process. These heating elements are frequently Ice Summary of the invention This invention is directed at providing a transducer which is capable of rapid response over wide ranges of ambient temperatures and which is activated by an electrical element located within the heat responsive material, said element being mounted and terminated in a very simple manner. There is also included as part of the invention a unique method of sealing the piston end of the transducer.

Description of the drawing FIG. 1 is a side elevation of the electromechanical transducer;

FIG. 2 is a section on line 2-2 of FIGURE 1; FIG. 3 is a top plane view of the heating element used in the heat motors shown in FIGURE 1; and

FIG. 4 is a section showing the electromechanical transducer of FIGURE 1 in an automotive heater control system.

Description of the preferred embodiment In the drawing, particularly FIGURES 1 through 3, there is shown a housing 2, generally tubular in configuration, and having a mounting collar 4, integral therewith, whose external diameter is greater than the remaining portion of said housing 2, and which defines an internal shoulder 6, for a purpose to be described hereinafter. Said housing 2, is open at both ends and includes a second internal shoulder 8, proximate to the opening remote from the mounting collar 4. A terminal 10, having a shank portion 12, extending from a circular head 14, as shown in FIGURE 2. The heater element 16, comprises a helical wire form having at one end a comparatively small diameter hook termination 18, and having at the other end a comparatively large diameter loop termination 20. The insulator 22, is formed of delrin or nylon having an axial bore 24, formed through a circular base portion 26, and having a medial extension 28.

The heater subassembly comprises the terminal 10, the insulator 22, and the heater element 16. To assemble the heater subassembly the shank portion 12, of the terminal 10, is passed through the loop termination 20, of the heater element 16, until the hook termination 18, butts against the upper surface of the base portion 26, while partially circumscribing the shank portion 12. The shank portion 12, is then pressed through the axial bore 24, of the insulator 22, until the base portion 26 comes into close proximity to the head 14, of the terminal 10, and the hook termination 18, is sandwiched therebetween as shown in FIGURE 2. The heater assembly is now placed within the housing 2, and the shank portion 12, and theexte'nsion 28, are I passed through the aperture adjacent the second inteinal shoulder 8, until the undersurface of the base portion 26, is in superimposed butting relationship with the shoulder 8. This provides a press fit seal between the housing 2, and the heater subassembly.

An insulating sleeve 30, is inserted into the cavity of the housing 2, against its inner surface for a purpose to be explained hereinafter. The loop termination 20, of the heater 16, is in a butting relationship with the shoulder 6, and upon completion of the assembly will form an electrical connection therewith. The seal element 32, which is generally flat, circular, washer-like in configuration and has an axial hole 34, formed therethrough whose diameter is considerably less than the diameter of the shaft or piston 36. The shaft or piston 36, is a rod-like member. The inventors have discovered that a tapered configuration is not necessary on the terminal end of the shaft 36. The piston36, is engaged to the seal element 32, by passing it through the hole 34, making an extremely tight press fit and distorting the seal element 32, into a truncated cone as shown in FIGURE 2. In operation, internal pressure tends to flatten this cone-shaped seal element 32, thus compressing the seal tightly around the shaft, 36.

A guide element 38, comprising a tubular body portion 40, having a flange 42, extending radially therefrom, adjacent an open end thereof. The shaft subassembly of the seal element 32, and the shaft 36, is engaged with the guide element 38, by passing the shaft 36, through the bore of the body portion 40, until the flange 42, butts against the concave surface of the. seal element 32. It is important that the shaft 36, can move axially within the body portion 40, without distorting the round shape of the hole 34, in the seal element 32. The shaft subassembly is passed into the housing 2, with the seal element 32 in close proximity to the internal shoulder 6, and the loop portion 20, of the heater element 16. The portion of the shaft 36, below the plane of its engagement with the seal element 32, is passed down through the heater element 16, and is circumscribed thereby. The free terminal edge of the mounting collar 4, is now crimped downwardly and inwardly to set itself against the upper surface of the flange 42, thereby fixing the total assembly.

The thermel material 44, utilized in the heat motor, is a synthetic wax which melts at a temperature above 210 degrees Fahrenheit. The wax is placed in the housing by first removing the shaft 36, and then pumping the material through the bore of the guide element 38. When the cavity of the housing 2, is filled with the wax, a shaft 36, is replaced and the heat motor is ready to be placed in an assembly. A lubricant, which is poorly soluble in the synthetic wax 44, is mixed with the wax 44, at the time that it is injected into the housing 2. The inventors have discovered that to the best of their knowledge, all of the thermal expansion materials tend to cling to the shaft and be drawn from the cavity unless extraordinary precautions are taken. The lubricant wets all internal surfaces of the device, including that portion of the shaft 36, inside the case. The combination of the seal configuration and the lubricant form an effective yet quite simple barrier to the wax.

The insulating sleeve 30, is used to prevent the heating element 16, from engaging and shorting against the side of the housing 2, which is formed of a conductive ma terial. However, the inventors have discovered that it is not absolutely necessary that an insulating sleeve be included, since the synthetic wax 44, is nonconductive and the physical support of the heater element at each end is suflicient to prevent the helix from touching the housing 2.

Electromechanical transducers of the type disclosed herein by the applicant can be used in many varying applications in'automotive equipment, aviation, home appliances and home equipment, such as window blinds, home heating equipment,-ventilation dampers and airconditioning equipment. A typical application is shown somewhat diagrammatically in FIGURE 4. This discloses themo'dulati'on of a hotaiid cold fluid stream by an electromechanical transducer. The heat motor 1, is mounted in a bracket 46, with the mounting collar 4, butted against the flange of the bracket, and a trip plate 48, which includes, if necessary, a spring guide attached to the free end of the shaft 36, which extends beyond the guide element 38. A compression spring 50, is engaged with the trip plate 48, and around the spring guide at one of the ends, and at the other end circumscribes a secondary shaft 52, which is connected to the trip plate 48, and which passes through a portion of the bracket or mounting means and is connected to a joint 54, which in turn, is connected to a blending baffle 56, through a shaft. The joint 54 is a mechanism for converting linear motion to angular motion. In the embodiment shown there are two conduits, the first being a conduit 58, for conducting relatively hot fluids or gas, and the second conduit 60, being one for conducting relatively cold fluids or gas. There is also disclosed a blended fluid or outlet conduit 62, which accepts the fluids from the hot conduit 58, and cold conduit 60, and passes the mixture, if any, on to the final application.

In operation, the position of the blending baffle 56 is controlled by the heat motor 1, according to the relative amount of hot and cold fluid demanded by the requirements of the final application. This demand can be relayed to the heat motor quite easily. A bimetallic contact (not shown) located in the outlet conduit 62, in series with the heat motor and a power source can control the position of the heat motor directly. The on-off action of the bimetal contact is smoothed by the response of the heat motor yielding an even, proportional positioning of the blending baflle. A contact leaf 64, of a limit switch 66, is positioned between the trip plate 48, and the upper end of the bracket 46. The position of the limit switch 66, is adjusted such that the trip plate 48, opens the'electrical circuit at the intended limit of piston travel. In other words, the limit switch 66, stops the motion of the baffle 56 when it contacts the cold conduit 60, thereby preventing over extension of the transducer. During this action the compression spring 50 is placed under increasing compressive forces and when a cooler fluid mix is required the pressure of the wax on the piston 36 is relaxed by reducing the heat outputof the heater element 16. This reduction of pressure allows the spring 50 to expand and, in effect, pulls the shaft 52, back toward the heat motor 1, and thereby moving the blending baffle 56, toward the hot conduit 58.

The inventors have simplified the control so that three elements, namely, an electrically activated transducer, a bimetallic contact and a-power source form a low cost, high gain closed loop servo system for the control mixing of fluids.

With reference to the foregoing description it is to be understood that what has been disclosed herein represents only a single embodiment of the invention and is to be construed as illustrative rather than restrictive in nature and that the invention is best described by the following claim.

We claim:

1. A transducer comprising a housing defining a cavity and having a terminal means extending therefrom, said housing having a thermally responsive material therein and an open end, said open end of said housing being partially closed off by a seal element having an aperture formed therethrough, a shaft means passed through said aperture into the thermally responsive material, an electrically actuated heater means, embedded in said thermally responsive material, circumscribes a portion of said shaft means, said shaft means adapted to move relative to said seal element in response to the expansion of said thermally responsive material, said heater means generally helical in configuration and having a looped termination formed at one end thereof in abutting relation with an' internal shoulder formed in said housing, and means for 5 holding said seal element in engagement with said housing, said terminal means spaced from said housing by an insulator and including a head portion and a shankextending therefrom and said insulator comprising a base portion and a medial extension extending from said base portion, said base portion and said medial extension having an axial bore formed therethrough, and a terminal end of said heater element sandwiched between the head of said terminal and the base portion of said insulator and the shank of said terminal extending through said axial bore of said insulator.

References Cited UNITED STATES PATENTS MARTIN P. SCHWADRON, Primary Examiner. 0 CARROLL B. DORITY, Assistant Examiner. 

